The present invention relates to a differential locking or limiting apparatus of a planetary gear type differential for locking up a differential between a carrier and a shaft member provided with a sun gear.
A variety of differential locking apparatuses in which two of input and output shafts can be locked up with each other have been proposed to date. Generally, these differential locking apparatuses are constituted by a multiple disc clutch provided between two of input and output shafts and a differential limiting mechanism for pressing the multiple disc clutch when a differential rotation generates between these two shafts. For example, Japanese Paten Unexamined Publication No. Hei. 1-278841 discloses a differential locking apparatus of a planetary gear type center differential comprising a multiple disc clutch provided between front and rear wheels and a ball cam for pressing the multiple disc clutch when a differential rotation generates between the front and rear wheels.
However, the differential locking apparatus having the multiple disc clutch and the differential limiting mechanism incurs a complication of the apparatus and an up-sizing of the apparatus. Particularly since the multiple disc clutch is constituted by a plurality of drive and driven plates arranged in the axial direction, the up-sizing in the axial direction is noticeable.
Further, conventionally, a differential is provided with a differential limiting apparatus which adds a differential limiting torque as an initial torque in advance, or bypasses and transmits a torque to the other output shaft when one output shaft slips.
This sort of differential limiting apparatus is generally constituted by a hydraulic multiple disk clutch, and for example, Japanese Patent Unexamined Publication No. Hei. 5-112149 discloses a technique in which in a planetary gear center differential, a hydraulic multiple disk clutch is provided between a carrier and a rear drive shaft, and a differential limiting torque is generated in the hydraulic multiple disk clutch in accordance with a rear wheel slip.
However, since the hydraulic multiple disk clutch is generally constituted in such a manner that a plurality of drive plates and driven plates are arranged, there is a fear that a device becomes complicated and large-sized.
It is an object of the present invention to provide a differential locking or limiting apparatus for a planetary gear type differential having a small size and simple structure.
In order to attain the object, a planetary gear type differential apparatus provided on a shaft member and having a carrier rotatably mounted on said shaft member, a sun gear secured on the shaft, a pinion meshing with the sun gear, and a pinion shaft secured to the carrier for rotatably supporting the pinion. The differential apparatus comprises a sliding surface provided on the shaft, a projection formed at an end portion of the pinion-shaft and projected from an end surface of the carrier, and a cam member including a friction surface slidable on the sliding surface and a V-shaped groove engageable with the projection and provided between the sliding surface and the projection.
That is, according to the invention, when a differential occurs between the shaft member and the carrier, the cam member relatively moves with respect to the carrier by frictional resistance of the friction surface against the sliding surface and the position where the projection is engaged with the V-shaped groove deviates. According to the deviation amount of the projection with respect to the groove, a pressure toward the sliding surface generates in the cam member and the frictional resistance of the friction surface against the sliding surface is increased to perform a differential between the shaft member and the carrier. When the amount of the positional deviation of the projection with respect to the V-shaped groove further increases, the relationship between the shaft and the carrier is locked due to the wedge effect of the friction surface.
In addition to this, the above-mentioned object can be achieved by a planetary gear type differential apparatus provided on a shaft member and having a carrier rotatably mounted on said shaft member, a sun gear provided at the shaft portion, a pinion engaged with the sun gear, and a pinion shaft for rotatably supporting the pinion to the carrier, the differential apparatus according to the present invention comprising:
an annular sliding portion provided on the shaft member;
a projection formed by protruding an end portion of the pinion shaft from an end surface of the carrier;
a cam member disposed between the sliding portion and the projection, the cam member including a friction surface that is slidably engaged with the sliding portion and a V-shaped groove that is engageable with the projection; and
a pair of restriction sections which are formed at an end surface of the carrier and disposed at both sides of the cam member, each of the restriction sections regulating the movement of the cam member in a rotational direction of the carrier while a predetermined swing motion is permitted.
According to the invention, when a differential movement is occurred between the shaft member and the carrier, the cam member is moved relatively to the carrier between the restriction sections by friction resistance of the friction surface with respect to the sliding portion. At that time, an engagement position of the V-shaped groove with respect to the projection is shifted. In accordance with the shifting amount of the engagement position of the V-shaped groove relative to the projection, a press force in the direction toward the sliding portion is generated at the cam member, and the friction resistance of the friction surface with respect to the sliding portion is increased. Therefore, a differential limitation is made between the shaft portion and the carrier.
With this structure, the cam member is positioned at the inner periphery of the sliding portion, and the press force by a centrifugal force in the direction toward the sliding portion is applied to the cam member.
In the above-mentioned structure, it is preferable that the shaft member comprises:
a shaft; and
a drum member fixed to the shaft and having an inner periphery on which the sliding portion is formed.
In the above-mentioned structure, it is preferable that the shaft member comprises:
a shaft having an outer periphery on which the sliding portion is formed.
Further, in the above-mentioned structure, it is also preferable that the shaft member comprises:
a shaft; and
a ring member coupled with the shaft and having an outer periphery on which sliding portion is formed.
With the structure, the cam member is positioned at the outer periphery of the sliding portion, and a force to cancel the press force in the direction toward the sliding portion by a centrifugal force is applied to the cam member.
Moreover, in the above-mentioned structure, it is advantageous to further comprise an energizing member urging the cam member towards the sliding portion.
With this structure, an initial torque in the planetary gear type differential can be generated.